Conventional microphones include a transducer that converts sound into an electrical signal. Most microphones use electromagnetic induction, capacitance change, or piezoelectricity to produce an electrical signal from air pressure variations. Microphones typically need to be connected to a preamplifier before the signal can be recorded or reproduced.
A microphone can be configured to detect sound from different directions (i.e. have different polar patterns). Some microphones are omnidirectional, meaning that sound can be detected from any direction. However, conventional omnidirectional microphones cannot isolate sound from a particular direction. Unidirectional microphones are sensitive to sound from only one direction. However, use of unidirectional microphones may be cost prohibitive in consumer products.